Fertilizer blade assemblies are employed by farmers to deliver nitrogen enriching fertilizers such as anhydrous ammonia to a targeted zone beneath the surface of the soil of a crop field while causing a minimum of disruption to the structure of the upper layer of the top soil. Fertilizer blade assemblies are often used by farmers who are practicing “low till” agriculture. Low till agriculture is a method of farming in which the disturbance of the soil is kept to a minimum. By preserving the structure of the upper layer of top soil, farmers can protect the moisture retaining capacity of the soil and also make it easier for new crop plants to put down roots. Typically, fertilizer implements carry patterns of fertilizer blade assemblies spaced for simultaneously delivering fertilizer to a plurality of parallel furrows.
Prior art fertilizer applicator blades are typically one piece structures having a shank plate with a blade portion. The shank plate is typically an elongated steel plate which, when in use, slants down and forward into the soil and is usually bolted to one of a plurality of the bracket pieces of a fertilizer implement. A typical prior art blade portion is either integral with the shank plate or permanently welded to the shank plate and provides a hard sharp leading edge. A fertilizer tube is also welded to the trailing edge of the shank plate. The fertilizer tube terminates at the base of the shank plate and delivers liquid fertilizer to the furrowed soil at that location as the applicator blade assembly cuts through the soil. With prior art fertilizer applicator blades; when part of the fertilizer applicator blade is too worn for use, the entire blade is removed and replaced.
The design and function of a fertilizer blade presents a difficult challenge for designers. The cost of fuel for powering tractors which pull fertilizer implements has increased greatly in recent years. The cost of steel used for making replacements for worn fertilizer blades has also recently increased substantially. Since the early 1970's, as of the filing date of this application, the cost of anhydrous ammonia fertilizer has increased by approximately a factor of ten after correcting for inflation. Accordingly, what is needed is a fertilizer blade assembly which minimizes the waste and loss of fertilizer, which may be inexpensively reconditioned for use when worn, which minimizes the amount of energy required to pull the blade assembly through soil.